Question

A small piece of wood is floating on the surface of a 2.5 m deep lake. Where does the shadow form on the bottom when the sun is just setting ? Refractive index of water $=\frac{4}{3}$.

Answer 1

Height of the lake = 2.5 m

When the sun is just setting, q is approximately = 900

$\therefore \frac{sini}{sinr}=\frac{{\mu }_2}{{\mu }_1}$

$\Rightarrow \frac{1}{sinr}=\frac{\frac{4}{3}}{1}$

$\Rightarrow sinr=\frac{3}{4}\Rightarrow r={49}^{\circ }$

Thus, $\left(\frac{x}{2.5}\right)=tanr=1.15$

$\Rightarrow x=2.5\times 1.15=2.8\text{m}$